Quiz 2 (Ch. 5 & 6)

Question 1

Maternal Effect

Answer 1

Offsprings’ genotypes do not determine their own phenotypes. The mother’s genotype determines the offspring’s genotype.

Question 2

Epigenetic Inheritance

Answer 2

Genes or chromosomes are altered (ex: silenced) during gametogenesis or embryogenesis. Alteration is not permanent over the course of several generations

Question 3

X-chromosome inactivation

Answer 3

Silencing of one X chromosome during embryogenesis in somatic cells of females. Results in a Barr body

Question 4

Genomic imprinting

Answer 4

Silencing of a gene during oogenesis or spermatogenesis, but not both

Question 5

Extranuclear inheritance

Answer 5

• Some genes are found in mitochrondrial or chloroplast DNA

- The segregation of these organelles does not obey Mendel’s Law of Segregation

Question 6

Linkage

Answer 6

• Two or more different genes may be located close together on the same chromosome
• These close genes do not obey Mendel’s Law of Independent Assortment

Question 7

Dosage compensation

Answer 7

The phenomenon that the level of expression of many genes on the sex chromosomes (such as
the X chromosome) is similar in both sexes even though males and females have a different complement of sex chromosomes

Question 8

Barr body

Answer 8

A highly condensed structure that is composed of the inactivated X-chromosome in female mammals

Question 9

True/False: In a given human female cell, whichever X chromosome was inactivated from the initial parent cell is the X chromosome which continues to be inactivated in all future generations of that same cell

Answer 9

True; The initial process of inactivation is random among all cells, however (except in marsupials, which always have the paternal X inactivated)

Question 10

X-Inactivation Center (XIC)

Answer 10

Portion on the X chromosome which determines whether that chromosome will be inactivated or not; Contains the Xist and Tsix genes

Question 11

Xist gene

Answer 11

• X-Inactive Specific Transcript
• Coats the X chromosome and inactivates it
• Other proteins associate with this coating and convert the X-chromosome into a barr body

Question 12

Tsix gene

Answer 12

• Gets its name from being ‘Xist’ backwards

- When expressed, inhibits expression of the Xist gene and therefore prevents x-chromosome inactivation

Question 13

X Chromosomal Controlling Element (XCE)

Answer 13

-Region on X chromosome which contributes to deciding which X chromosome will be inactivated

Question 14

Maternal inheritance (NOT maternal effect)

Answer 14

• When there are genes which only exist in the egg, not in the sperm, and can therefore only be passed to future generations through the mother
• Ex: In the four-o-clock plant, the chloroplasts only exist in the egg – the pollen does not contain any chloroplasts
• Occasionally, paternal leakage occurs, in which some paternal extranuclear DNA is found in the offspring

Question 15

Locus

Answer 15

The location of a gene on a chromosome